Buzz
Referred to as the 'couch potato of the shark world,' the nurse shark (Ginglymostoma cirratum) enjoys a leisurely lifestyle. During the day, it rests, and at night, it prowls the sandy seabeds and coral reefs of its shallow-water domain, feeding on small creatures it encounters.
Despite its relaxed pace and gentle nature, it's important to give the nurse shark plenty of space. Reckless behavior around this species can lead to serious injuries. Here are 13 essential facts every ocean enthusiast should know about nurse sharks.
1. IT BREATHES USING A TECHNIQUE CALLED BUCCAL PUMPING.
For some shark species, resting on the ocean floor is impossible. Sharks like the great white and the whale shark rely on continuous movement to breathe; as they swim, water flows into their mouths and over their gills, delivering oxygen. If they stop moving, the water stops flowing, and they suffocate. However, other species, including the nurse shark, can breathe while staying still. By using oral muscles to actively suck water into their mouth—known as buccal pumping—it can supply oxygen to its gills without needing to swim.
2. THEY CAN "WALK" ON THE OCEAN FLOOR.
Nurse sharks are typically found in shallow coastal waters. These nocturnal hunters often search for food within 65 feet of the surface (though adults may rest in deeper waters during the day). Their habitat is mostly around coral reefs and coastal shelves, where they hunt along the ocean floor, seeking prey in or near the sand. Instead of swimming, they sometimes use their pectoral fins to 'walk' across the bottom.
3. THE SMALL KNOBS ON THEIR FACES ARE CALLED “BARBELS.”
Barbels are fleshy sensory organs that contain taste buds, which they drag across the sand in search of prey.
4. THEY SUCK UP THEIR FOOD.
Nurse sharks feed on a range of sea creatures, from conchs and squid to sea urchins and bony fish. A specialized cavity in their throat creates strong suction that 'vacuum' unsuspecting animals into the shark’s mouth, where rows of tiny, backward-curving teeth crush the prey.
The shark's mouth operates like a conveyor belt for its teeth. New rows of teeth emerge from the back and gradually push the older ones forward until they fall out. The rate at which teeth are replaced depends on the season. During winter, a fresh row of teeth appears every 50 to 70 days, while in the summer, this process speeds up, with a new row appearing every 10 to 20 days.
5. THE SPECIES COMES IN SEVERAL COLORS.
Adult nurse sharks are typically brown, although they can also appear grey or yellowish. In 1992, a 'milk white' nurse shark with brown spots was captured and photographed near Key Largo, Florida. This shark might have had a condition called piebaldism, which resembles albinism. Piebald animals have patches of white skin mixed with normally pigmented areas. A similar adult nurse shark was filmed in 2014. While adult nurse sharks generally lack spots, young sharks are covered in small black dots that gradually fade as they mature.
6. THEY ENJOY RELAXING IN LARGE GROUPS.
Shark snuggle parties are real! During the day, the nocturnal nurse shark becomes inactive and spends hours lying still, pumping water over its gills. Popular spots for these rest sessions include crevices, ledges, and piles of rocks. While they don't socialize during hunts, nurse sharks often rest together in groups, with as many as 40 sharks piling on top of each other.
7. ADULTS CAN GROW OVER 10 FEET LONG.
The maximum recorded length for this species is 10.1 feet. As for weight, the heaviest nurse shark ever recorded by the International Game and Fish Association weighed 263.8 pounds. This shark was caught by a father and his 15-year-old son in 2007. Newborn pups measure 7.8 to 12 inches long, and premature nurse shark pups measured by scientists after birth weighed between 4.2 and 5.3 ounces each. Big things often start small.
8. THE ORIGIN OF THE NAME “NURSE SHARK” REMAINS A MYSTERY.
It’s certainly not trained to look after hospital patients, so why do we call this barbel-faced sea creature the 'nurse' shark? The origin of the name is a linguistic mystery, though historians have some theories. Perhaps sailors found that the suction-based feeding habits resembled the way nursing infants feed. Alternatively, the word 'nurse' could come from 'huss,' an old term for a different family of bottom-dwelling sharks (now known as 'catsharks'). Over time, 'huss' evolved into 'nuss,' which referred to a 'shark' or 'large fish.' So, the nurse shark name might be a linguistic twist on 'nuss.'
9. THE WHALE SHARK IS A CLOSE RELATIVE.
Reaching lengths of nearly 40 feet and weighing several tons, the adult whale shark is the largest fish alive today. Like the nurse shark, it feeds by suction, but the similarities don’t end there. Both the whale shark and the nurse shark belong to the order Orectolobiformes, which includes 39 species of sharks, mostly found in temperate and tropical oceans. Also known as 'carpet sharks,' these species are characterized by small mouths that don’t extend behind the eyes when seen from the side. All of them have two dorsal fins and five sets of gill slits. Many species in this order display striking skin patterns, with the nurse shark being a notable exception. Barbels are another shared trait.
The strangest member of the Orectolobiformes group may be the wobbegong sharks, which lie motionless on tropical sea beds and use excellent camouflage to ambush unsuspecting fish below.
10. NURSE SHARKS ARE PARTIALLY MIGRATORY.
Many well-known sharks make long migrations; every summer, hundreds of whale sharks from the Atlantic visit Mexico’s Yucatan Peninsula, and Pacific great whites embark on winter journeys to a mysterious, mid-ocean location called the 'White Shark Café.' Nurse sharks, however, are less inclined to wander; most stay in the same general area throughout the year.
However, some nurse sharks may still feel the urge to travel. In January 2018, the journal Environmental Biology of Fishes published a 23-year study on nurse shark movements. Scientists tracked a population that uses the Dry Tortugas in the Florida Keys as a mating ground. Of the 76 adult nurse sharks tagged, some stayed in the Dry Tortugas and nearby islands year-round. Others traveled as far north as Tampa Bay between mating seasons, making them 'partially migratory.' This means that while some nurse sharks migrate, not all do.
11. FEMALES DON’T GIVE BIRTH EVERY YEAR.
Nurse shark mating season spans from May to July, during which females mate with multiple males. Sometimes, several males will compete to mate with the same female, leading to aggressive 'shoving matches.'
Nurse sharks have a gestation period of five to six months and give birth to litters of 20 to 40 live pups. A single batch of pups may have up to six different fathers. After giving birth, a female nurse shark will not mate again for another 18 months.
12. BE AWARE: IT CAN DELIVER SEVERE BITES!
Don’t underestimate this creature. Nurse sharks are often seen as harmless due to their slow nature, their common presence in aquariums, and their small teeth. Many swimmers and divers in their natural habitat assume they are not dangerous. However, these sharks can crush clams with their teeth and create enough suction to yank a full-grown conch out of its shell—so don’t risk having one latch onto your arm.
That’s exactly what happened to a swimmer in Boca Raton, Florida, in 2016. The 23-year-old woman, snorkeling with friends, had her right arm clamped onto by a 2-foot-long nurse shark. (Eyewitnesses claimed the shark had been harassed by another group of beachgoers.) The shark stayed latched on while the swimmer was taken to the hospital, where she survived, but the shark perished before the medical team arrived. In another incident in 2018, an Instagram model was bitten while posing in shallow waters inhabited by nurse sharks.
While nurse shark attacks are rare, they are far from unheard-of, and humans are often to blame. YouTube is full of videos where divers are seen hugging, grabbing, or petting wild nurse sharks. Despite their typically docile and shy behavior, these sharks may bite if provoked—or if they mistake an arm or finger for food.
“People are playing with fire,” George Burgess, director of the International Shark Attack File, remarked to the Palm Beach Post. In an interview with Newsweek, he explained that “A nurse shark bite is one of the worst, because their teeth are like cheese graters on each side. When they latch onto a human, it’s like a vacuum cleaner… They leave a concave hole where they’ve turned flesh into hamburger.”
13. A NEW SPECIES OF NURSE SHARK HAS BEEN RECENTLY IDENTIFIED.
Ginglymostoma cirratum is commonly found in the Caribbean, off the northeastern coast of South America, near Spain, along western Africa, and by the eastern coast of the U.S. However, a 2012 study discovered that a population residing in the tropical eastern Pacific is genetically and anatomically distinct enough to be classified as a separate species. This new species, Ginglymostoma unami, or the Pacific nurse shark, displays certain features that differentiate it from G. cirratum. One such feature is the position of its second dorsal fin, which is located closer to the tail. The separation of the two species is believed to have occurred around 3 million years ago, when tectonic plate movements isolated the ancestral nurse shark populations on either side of the Panamanian land bridge.
